Calcium Chloride Activation of Mung Bean: A Low‐Cost, Green Route to N‐Doped Porous Carbon for Supercapacitors

Abstract N‐doped porous carbons were prepared from mung bean flour by chemical activation with calcium chloride and urea. Adjusting the precursor and preparation temperature had significant effect on the graphitization, specific surface area, porosity and surface chemical composition of the porous carbons. The material prepared from the mixture of mung bean flour, urea, and calcium chloride at 800 °C was the optimal sample. It exhibited an excellent specific capacitance (247.2 F g −1 at 2 mV s −1 and 300.5 F g −1 at 1 A g −1 , respectively), outstanding rate performance (178.6 F g −1 at 200 and 225 F g −1 at 100 A g −1 , respectively) and good durability (93.2 and 97.5% capacitance retention after 10000 cyclic voltammograms and 2000 galvanostatic charge/discharge, respectively) in 6 M KOH. The structure‐performance relationships reveal that the excellent specific capacitance of this sample arises from its plentiful porosities, abundant doped‐N and high carbonation.